Download The Continuity of Life

The Continuity of Life
Mrs Tagore
Chromosomes and Eukaryotes
Read pages 15-16
Chromosomes and Eukaryotes
Read pages 15-16
Chromosomes and Eukaryotes
Read pages 17-18
Chromosomes of Prokaryotes
Read pages 18-19
Questions
• Complete questions 1-10 for tomorrow.
• We will be discussing these in class, so I’ll be
checking that you have done it!!
Title: Mitosis
Learning question: What are the names of the stages of
mitosis?
Hook: What connects these pictures?
(Can you write more than one word?!)
Lesson Aims
• Describe the cell cycle
• Understand that mitosis is only one small part of
the overall cell cycle
• State the events that occur at each phase of the cell
cycle
• Describe each stage of mitosis
• Identify each stage of mitosis from diagrams and
micrographs
Cell division
•All complex organisms
originated from a single
fertilised egg.
•Every cell in your body
started here, through cell
division the numbers are
increased.
•Cells then specialise and
change into their various roles
Mitosis
• Mitosis is the process by which new
body cell are produced for:
– Growth
– Replacing damaged or old cells.
This is a complex process requiring is to be
split into different stages to understand
it.
DNA
• ‘Blueprint of life’
• Codes for all the proteins needed for life
• Describes that characteristics of every
living thing
• Every cell with a nucleus contains ALL the
instructions to make the organism
• http://www.pbs.org/wgbh/nova/photo5
1/media/journey.swf
Chromosomes
• Each DNA strand is split into chromosomes
• All sexually reproducing animals have pairs of
chromosomes. One set of each pair comes
from each parent
–
–
–
–
–
Humans have 23 pairs
Lions have 19 pairs
African wild dogs have 39 pairs
Mosquito have 3 pairs
Some ferns have 500-600 pairs
This (imaginary, example) animal has just two pairs of
chromosomes
Red = Maternal
Blue = Paternal
1p
1m
2p 2m
During Interphase, each chromosome replicates and produces an
exact copy of itself:
1p + copy
1m + copy
2p + copy
2m +copy
There are four stages to Mitosis
 Prophase
 Metaphase
 Anaphase
P
M
A
T
 Telophase
 Remember though that this is a continuous
process
Interphase
 Standard condition
of cell
 DNA replicates
 Cell enters
reproductive cycle
with 2 copies of
each chromosome
Prophase
• DNA super coils
and
chromosomes
become visible
• Nuclear
membrane
breaks down
• Centrioles
migrate to
poles
Metaphase
• Chromosomes
line up
centromeres on
equator of cell
• Centrioles form
spindles
Anaphase
• Spindles ‘grip’
centromeres
and
chromosomes
migrate to
poles
Telophase
• Nuclear
membranes
reform
• Chromosomes
disperse
• Cytokinesis
begins
Interphase
• Both daughter
cells are exact
copies of the
parent cell
INTERPHASE
Stages of Mitosis
• http://www.cellsalive.com/mitosis.ht
m
1.
In humans, each cell (except sex cells) has how many chromosomes?
______
2.
After mitosis, how many daughter cells are produced? _______. After
mitosis (in a human cell), each daughter cell has how many chromosomes?
_____
3.
How many phases are in MITOSIS? ___________
4.
Which phase of the cell cycle is the longest? _________
5.
During which phase does cytokinesis begin? __________
6.
What cell parts migrate to the poles during prophase? __________________.
7.
What structure holds the two chromatids together? ____________________
8.
During which phase does the nuclear membrane dissolve?
__________________
9.
What structure moves the chromosomes into position and then pulls them
apart? ___________________
10. What is the overall purpose of mitosis? _________________________
Name the stages!
Binary fission
Binary fission
• Prokaryotes reproduce by binary fission
• No nucleus, centromere or chromosomes, therefore no mitosis
• Two daughter cells produced
• Cell replication>new DNA attaches itself to different part of cell
membrane>cell pulls apart separating replicate and original
DNA> wall forms dividing cells into two cells with identical
genetic composition
• Mitochondria and chloroplasts also use binary fission to form
new organelles